Hyaluronic acid (HA)

Hyaluronic acid (HA)

Hyaluronic acid (HA) is a naturally occurring substance in the human body, widely known for its role in skin hydration but with much broader biological functions.

What it is

HA is a glycosaminoglycan — a long chain of repeating sugar molecules (a type of polysaccharide). It’s found throughout the body, especially in:

• Skin (about 50% of the body’s total HA)
• Joints (synovial fluid)
• Eyes (vitreous humor)
• Connective tissue

Key property

Its defining feature is an extraordinary capacity to bind and retain water — up to 1,000 times its weight. This is what makes it so central to tissue hydration, cushioning, and lubrication.

Functions in the body

• Skin: Maintains hydration, volume, and elasticity; naturally declines with age (a major factor in skin aging/wrinkling)
• Joints: Acts as a lubricant and shock absorber in synovial fluid, cushioning cartilage during movement
• Wound healing: Plays a role in tissue repair and regulating inflammation
• Eyes: Found in the vitreous gel, helping maintain eye shape and cushioning

Common uses

• Skincare: A staple ingredient in moisturizers, serums, and masks for hydration; molecular weight affects how deeply it penetrates (higher MW sits on the surface, lower MW penetrates deeper)
• Dermal fillers: Injectable HA (e.g., Juvederm, Restylane) is used cosmetically to add volume, smooth wrinkles, and contour facial features
• Joint injections: Used medically (viscosupplementation) for osteoarthritis, particularly in the knee, to supplement natural joint fluid
• Eye surgery: Used as a lubricant/protective agent during procedures like cataract surgery
• Oral supplements: Marketed for skin and joint health, though evidence for oral absorption/efficacy is more mixed than for topical or injectable use

Safety

HA is generally well-tolerated since it’s naturally found in the body, with a low risk of allergic reaction compared to many other injectable or topical compounds. Side effects from fillers/injections are typically related to the injection itself (swelling, bruising) rather than the HA itself. Hyaluronic acid (HA)